1. Field of the Invention
The present invention relates to injection molding apparatuses, injection molding methods, and molded-product manufacturing methods that form molded products by injection-molding by heating and cooling molds.
2. Description of the Related Art
With regard to apparatuses that perform injection-molding by using resin, such as plastic, a temperature adjustment of molds is important for maintaining the quality of molded products at a satisfactory level. In particular, the molding surface of a mold is preliminarily heated prior to injection-molding, and the mold is immediately cooled after the molding.
In the related art, Japanese Patent Laid-Open No. 11-277539 discloses an apparatus that reduces the heat capacity of a heating unit.
This apparatus is a mold heating apparatus that heats a mold, which is constituted of a core and an openable-closable cavity that forms a resin molding space when the mold is in a clamped state, and has the following configuration.
Specifically, the apparatus includes a pressing movable member that applies pressure to the core so as to bring the core into pressure contact with the cavity during a mold clamping process, and a stationary pressure-receiving member that comes into contact with the cavity, with which the core is in pressure contact, so as to receive a pressing force applied to the cavity.
The apparatus further includes a core separating unit that separates the core from the pressing movable member during a mold opening process, and a heating unit that uses radiation heat to simultaneously heat both the core separated from the pressing movable member during the mold opening process and the cavity separated from the stationary pressure-receiving member.
As another solution for reducing the heat capacity of a heating unit, Japanese Patent No. 4698676 discloses the following apparatus.
This apparatus includes a cavity mold and a core mold. The cavity mold has a cavity surface that forms a cavity into which a molten injection material is to be injected. The core mold has a core surface that forms the cavity when the molds are joined. The core mold is guided by a guide pin and is provided in a forwardly and backwardly movable manner so as to open and close the cavity.
The apparatus further includes an injecting unit that injects a molding material into the cavity during an injecting process, a hydraulic cylinder that moves the core mold in the forward and backward directions, and an injection controller that controls the injecting unit for injecting the material.
The core mold has the core surface and is separable into an intermediate core mold plate having a small thickness and a core mold support plate having a large thickness. The guide pin extends from the core mold support plate. When the core mold moves toward the cavity mold, the guide pin is inserted into a first guide hole formed in the cavity mold and is fitted to the intermediate core mold plate so as to limit the movement of the intermediate core mold plate to the forward and backward directions.
Furthermore, the apparatus includes a first elastic member installed between the intermediate core mold plate and the core mold support plate so that when the core mold is moved backward for opening the cavity, the intermediate core mold plate and the core mold support plate are elastically separated from each other.
Moreover, the apparatus further includes a first heater (i.e., a heater fitted in the intermediate core) that is disposed at a separation surface of the intermediate core mold plate and that heats the intermediate core mold plate, a first cooler that cools the core mold support plate, and a mold temperature controller that controls the operation of the first heater and the first cooler so as to control the temperature of the intermediate core mold during injection.
With the configuration according to Japanese Patent Laid-Open No. 11-277539 in the related art, the heat capacity of the heating unit for the core mold and the cavity mold can be reduced.
However, since the core mold and the cavity mold are simultaneously heated by using radiation heat, it is realistically difficult to heat the core mold and the cavity mold within a short period time by using radiation heat, which has low thermal conductivity.
With the method according to Japanese Patent No. 4698676, the core mold has a core surface and is separated into an intermediate core mold plate having a small thickness and a core mold support plate having a large thickness so that the heat capacity of the heating unit can be reduced.
However, in view of a thermal fatigue breakage due to a heat cycle caused by fitting the heater in the intermediate core mold plate, the thickness is increased to about 80 mm, thus making it realistically difficult to perform heating and cooling within a short period of time.
The present invention provides an injection molding apparatus, an injection molding method, and a molded-product manufacturing method that can heat and cool a mold within a short period of time when forming a molded product by injection-molding by heating and cooling the mold, thus allowing for improved quality of the molded product.